Basic aluminum halides (also referred to as aluminum halohydrates) have long been known to possess antiperspirant activity. These antiperspirant compositions are available in the form of polymeric compositions having the empirical formula: EQU Al.sub.2 (OH).sub.6-y X.sub.y
wherein X is chlorine, bromine or iodine and y has a numerical value from about 0.7 to about 3.
However, it is only in recent studies, as described in U.S. Pat. No. 4,359,456 (the '456 patent), that it has been shown by size exclusion chromatography that basic aluminum halides are composed of individual polymer bonds which pertain to different molecular weight groups of the compound. In these studies of basic aluminum halides obtained by conventional methods of preparation it was shown that it can further be broken down from high molecular weight polymers by diluting concentrated aqueous solutions thereof to lower aqueous concentrations with heat and/or aging at room temperature to produce more effective antiperspirants as shown in sweat reduction panel studies.
The '456 patent describes processes for the preparation of improved antiperspirant compositions of aluminum halohydrates, which involve heating a 2.5 to 8.5% aluminum by weight aqueous solution of an aluminum halohydrate of the formula: EQU Al.sub.2 (OH).sub.6-y X.sub.y nH.sub.2 O
where x is chlorine, bromine or iodine and y has a numerical value from about 0.7 to about 3 and n has a numerical value from about 0.8 to about 4, at a temperature of 50.degree. to 140.degree. C. for a period of time to impart to the aluminum product certain desired properties in respect of size exclusion chromatography test bands. The products thus obtained from these processes have good antiperspirant activity, but the processes do not provide compositions containing larger amounts of the lower molecular weight polymers with a narrow polydispersity which are believed to possess greater antiperspirant activity.
Zirconyl hydroxyl chloride and alumina chlorhydroxide containing compositions are also known to have antiperspirant activity as disclosed in Great Britain Patent No. 2,144,992, published Mar. 20, 1985, entitled "ANTIPERSPIRANTS" (the British Patent). The product is prepared by heating a 2 to 20% aqueous solution to the compounds to at least 50.degree. C. until a ratio of the heights of peak 4 to peak 3 as measured by gel permeation chromatography exceeds 2:1. The resulting product contains lower molecular weight polymers to increase efficacy, but is also has a wider polydispersity, a higher form of aluminum to zirconium glycinate complex and a lower cationic charge when compared to the novel composition. This is evident from higher molecular weight polymers found in peaks (1+2) as shown in the U.K. Patent No. 2,144,992. Moreover, the novel composition has been tested and shown to be more effective in reducing perspiration than the known product in clinical sweat reduction panel studies, where a substantial amount of reduction was observed with the novel product.